DC833A - Demo Manual

QUICK START GUIDE FOR DEMONSTRATION CIRCUIT 833
VLDO LOW NOISE LINEAR REGULATOR
LTC3026
DESCRIPTION
Demonstration circuit 833 is an ultra-low dropout
voltage supply using the LTC3026 linear regulator,
which comes in a small 3mm x 3mm 10-Pin DFN
package. The DC833 has an input voltage range
from 1.14V to 3.5V when the internal boost converter
is enabled, and a maximum input voltage of 5.5V
when an external source is supplied. The output
voltage range is between 0.4V and 2.6V, and it is capable of delivering 1.5A max. output current. The
0.4V reference of the LTC3026 allows DC833 to supply power to very low voltage applications. The
DC833 is also an excellent choice for post regulation
of step-down switching regulators, creating a high
efficiency low-noise supply. DC833 comes assembled with small ceramic capacitors, showing the
LTC3026 ability to maintain stability with ceramic
output capacitors.
Gerber files for this circuit are available. Call the
LTC Factory.
, LTC and LT are registered trademarks of Linear Technology Corporation.
QUICK START PROCEDURE
The DC833 is easy to set up to evaluate the performance of the LTC3026. For proper measurement
equipment configuration, set up the circuit according
to the diagram in Figure 1.
the remaining output voltage options: 0.8V,
1.5V, or 1.8V. Move the shunt in JP6 from the
EXT(ernal) position to the Boost (Regulator)
position (Remove the ext. 5V bias voltage).
Re-insert jumper JP5 shunt into the ON position. Just as in the 1.2Vout test, the output
voltage should read Vout +/- 2% tolerance
under static line and load conditions, and +/2% tolerance under dynamic line and load
conditions.
Please follow the procedure outlined below for proper
operation.
1.
Before proceeding to test, insert jumper JP5
shunt into the OFF position, insert jumper JP6
into the EXT(ernal) position, and insert a
shunt into jumper JP1 for 1.2V output.
2.
Apply 1.4V to Vin, and 5V to Vboost.
Note: The bias voltage, Vboost, must be between 4.5V and 5.5V for correct output regulation.
Insert jumper JP5 shunt into the ON position.
Measure Vout; it should be 1.2V+/-2%
(1.176V to 1.224V).
3.
Vary the input voltage from 1.4V to 5.5V and
the load current from no load to 1.5A. Vout
should measure 1.2V +/- 2% (1.176V to
1.224V).
4.
Insert jumper JP5 into the OFF position and
move the shunt from jumper JP1 into any of
5.
When finished evaluating, insert jumper JP5
into the OFF position.
Note - If the power for the demo board is carried in
long leads, the input voltage at the part could “ring”,
due to the inductance in the long leads. This ringing
could affect the operation of the circuit or even exceed the maximum voltage rating of the IC. To eliminate the ringing, a small tantalum capacitor (for instance, an AVX part # TAJW686M010R) was inserted
on the pads between the input power and return terminals on the bottom of the demo board. The
(greater) ESR of the tantalum will dampen the (possible) ringing voltage due to the use of long input leads.
On a normal, typical PCB, with short traces, the capacitor is not needed.
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QUICK START GUIDE FOR DEMONSTRATION CIRCUIT 833
VLDO LOW NOISE LINEAR REGULATOR
VBOOST must be between 4.5V and 5.5V for proper operation.
Figure1. Proper Measurement Equipment Setup
Figure 2. Measuring Input or Output Ripple
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QUICK START GUIDE FOR DEMONSTRATION CIRCUIT 833
VLDO LOW NOISE LINEAR REGULATOR
RMS Output Noise vs. Load Current
(10 Hz to 100 kHz)
160
Cout - 10 uF
Vout - 1.8V
140
Vout - 1.5V
Output Noise (uVrms)
120
Vout - 1.2V
100
Vout - 0.8V
80
60
40
20
0
0
250
500
750
1000
1250
1500
Load Current (m A)
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QUICK START GUIDE FOR DEMONSTRATION CIRCUIT 833
VLDO LOW NOISE LINEAR REGULATOR
Output Noise Spectral Density
1
Output Noise Spectral Density (uV/rootHz)
Vout = 1.2V
Iout = 1.5A
Cout = 10 uF
0.1
0.01
0.1
1
10
100
Frequency (kHz)
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QUICK START GUIDE FOR DEMONSTRATION CIRCUIT 833
VLDO LOW NOISE LINEAR REGULATOR
10 Hz to 100 kHz Output Noise (X-Axis Scale: 1ms/div; Y-Axis Scale: 200uV/div)
Vout = 1.2V Vboost = 5V Iout = 1.5A
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QUICK START GUIDE FOR DEMONSTRATION CIRCUIT 833
VLDO LOW NOISE LINEAR REGULATOR
LTC3025 Load-Step Response – Trace 1: Vout Ripple (20 mV/div) – Trace 2: Iout (1A/div)
Vin = 2V
Vout = 1.2V Vboost = 5V Istep = 1.5A Iout(min) = 20 mA
Cout = 10 uF Time Base: 50 us/div
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QUICK START GUIDE FOR DEMONSTRATION CIRCUIT 833
VLDO LOW NOISE LINEAR REGULATOR
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